New draft guidance to be published today by The National Institute for Health and Clinical Excellence (Nice) says as many as one in four people experience elevated blood pressures whenn their BP is taken in a GP’s surgery. This is known as “white coat hypertension” and can significantly raise blood pressure readings and as a result many people are being misdiagnosed.

Nice is now recommending that doctors do not rely solely on readings taken in their own surgeries. A patient should be sent home and asked to wear an ambulatory blood pressure monitoring (ABPM) device.

More than 8.5 million people are registered as having high blood pressure. People with the condition are three times more likely to develop heart disease and suffer strokes as people with normal blood pressure and twice as likely to die from these.

Nice’s guidance notes state: “White coat hypertension is reported to occur in as many as 25 per cent of the population, especially where their blood pressure is close to the threshold for diagnosis.”

This suggests that as many as 2 million people may have been wrongly diagnosed simply because they were nervous when they went into the surgery.

The Blood Pressure Association, which has been campaigning for the change for years, welcomed the move and said the guidance should be backed up with money “to ensure ambulatory monitors are more widely available”.

Nice officials said the guidelines would “significantly change the way high blood pressure is diagnosed and subsequently treated”.